Infrared source utilizing an exothermic chemical charge



Nov. 23, 1965 A. L. PITTINGER INFRARED SOURCE UTILIZING AN EXOTHERMIC CHEMICAL CHARGE Filed April 25, 1963 F/GZ.

o 9 4 5 3 E 3 4 4 V O 7 2 4 H INVENTOR: A. L. PITTINGER ATTORNEY Patented Nov. 23, 1965 3,219,827 INFRARED SOURCE UTILIZING AN EXO- THERMIC CHEMICAL CHARGE Abraham Lincoln Pittinger, Scottsdale, Ariz. (R0. Box 6, Tempe, Ariz.) Filed Apr. 25, 1963, Ser. No. 275,722 9 Claims. (Cl. 250-84) This invention relates to new and useful improvements in methods and apparatus for producing and emitting radiant energy, and more particularly to radiant sources in the infra-red spectrum.

Sources of radiation in the infra-red spectrum are useful as target devices, in testing equipment, and in training personnel in weapon systems having infra-red sensitive homing mechanisms.

Various devices for emitting radiant energy in the infra-red spectrum have been disclosed and claimed in U.S. Patent No. 2,933,317, issued April 19, 1960, to A. L. Pittinger et a1. These devices comprise essentially a black-body crucible, an exothermic charge contained in the crucible, igniting means for reducing the charge to a molten state, and'a radiating zone for infra-red rays on the crucible, said zone being defined by a wall adapted to contain substantially all of the molten charge.

The exothermic charge described in the prior patent comprises a finely divided granulated mixture of iron oxide and aluminum which, upon ignition, produces a pool of molten iron and slag, and which heats the crucible to a temperature in the range of 3000 degrees F. The infrared radiation which emanates from the crucible is propagated in substantially all directions.

The emissivities which may be achieved in accordance with the method referred to in the prior patent are usually less than unity. However, a higher emissivity and a directional radiation are very desirable objectives in the art of infra-red radiation.

It is, therefore, an object of the present invention to provide sources of infra-red ray emission in which the emissivity approaches unity.

It is a further object of this invention to provide sources of infra-red energy adapted to emit directional radiation.

A further object of this invention is to provide sources of radiant energy adapted to effectuate controlled or modulated radiation of the infra-red wave energy.

A still further objectof this invention is to provide improved methods in the 'art of preparing exothermic chemical charges for the generation of radiation in the infrared spectrum.

The above and other objects of the invention will be described further with reference to the accompanying drawing in which:

FIG. 1 shows a longitudinal axial section through one embodiment of the invention;

FIG. 2 represents a longitudinal axial section through a modified embodiment of the invention;

FIG. 3 is a cross section along line 3-3 of FIG. 2, and

FIG. 4 represents a cross section along line 44 of FIG. 2.

The radiant energy source Referring now more particularly to the drawings, FIG. 1 shows a source of radiant energy such as infra-red rays, comprising essentially a cylindrical metal casing 12 surrounding a similarly shaped thermal-insulating lining 14 of refractory material. An exothermic chemical charge 16 is contained within the space formed by the cylindrical refractory material 14, an inwardly extending graphite cone 17 and a disk-like member 18 which is composed of a gas quenching material. The latter ma- Cit terial is contained within the space formed by the refractory washers 20 and 22.

A closure 24, a hermetic sealing member 25, and a retaining ring 26 are provided as shown to insure a tightly fitting construction at one end of the device whereas graphite cone 17 with its annular collar 27 is securely fitted to the other end of the liner 14 and charge 16 to insure a gas tight joint. The opening angle of the cone 17 is preferably less than 90 degrees.

A metal tube 29 may be provided as shown for the purpose of evacuation of air from the interior of the device by means of a vacuum pump (not shown) so that substantially all the atmospheric air may be readily evacuated from the radiant energy source.

Electrical ignition means 28 are mounted upon the inner surface of the graphite cone 17, and electrical lead wires 30 are provided, said wires leading to a source of igniting electricity (not shown). The ignition device 28 may comprise an exothermic wire or it may be constituted by a separate encapsuled structure. The main exothermic charge 16 and the igniting charge 16a are composed of a compressed material described below, and during the exothermic reaction, the entire mass will be pervious to the hot gases traveling therethrough and, via duct 32, to the gas quenching materal 18.

FIG. 2 shows a source of infra-red radiant energy including a cylindrical metal container 42, an insulating sleeve 43, and an exothermic chemical charge 44, all of which may be substantially similar to that of FIG. 1. Also, the exothermic charge may have, in admixture therewith, a gas producing material. Adjacent to the conical cavity 46 there is provided a light duct 48 which is adapted to gather the scattered infra-red light such as schematically indicated by light beam 49, and imparting thereto a directional effect.

Cone 46 consists of graphite and has mounted upon it igniting charge 47 and electric ignition means 37 connectable by means of wires 35 to a source of igniting electricity (not shown).

A duct 50 of refractory material leads to a chamber containing a bed of heat absorbing material 55. Hermetic sealing means 60, closing collar 62, and resilient ring 64 on the one end of the assemblage, and annular collar structure 66, at the other end of the assemblage, constitute an air-tight seal of the entire radiant energy source.

Communicating with the chamber containing the heat absorbing material, there is provided a conduit which leads to a duct 72 containing a ceramic filter 74 in such a manner as to provide means for the gases from chamber 55 to be injected, through nozzle 76, into a gas turbine comprising rotor 82 and stator 81.

Rotor 82 is provided with reaction buckets 83 disposed on the periphery, and with a recess 84 (FIG. 3) adapted to receive an opitical reticle 86; this rotatable reticle in conjunction with an identical stationary reticle 88 in the stator serves to modulate the light rays such as ray 49 passing therethrough.

It may be desired to replace the gas turbine by a pistonoperated device, or any other device, for utilizing the energy of the gases of reaction in any desirable manner for any alternate purpose.

It may also be desired to replace the gas turbine with an electric or spring powered motor.

Operation The operation of the device of FIG. 1 is as follows: Upon application of a suitable electric current to the ignition circuit 30, the exothermic charge 16 is caused to react at a rapid rate, releasing a large amount of thermal energy substantially without the evolution of gaseous products. The graphite cone 17, is heated to incandescence within a very brief time period, i.e. of the order of one second, whereupon it emits infra-red energy from the conical cavity as a black-body emitter, free from any production of gas, smoke, flame, or sound, and its emissivity is close to unity. The peak temperature can be varied from about 1000 to 3000 degrees C., depending upon the relative amount of the charge.

The operation of the device shown in FIG. 2 is substantially as follows: Upon application of a suitable electric current to the ignition circuit 39, the exothermic charges 47 and 44 are caused to react, heating the entrapped air which enters the conduit 50 and is conducted to the bed of heat absorbing material 55 in which the temperature of the gas is reduced to a desired level. This gas or gas mixture is then conducted through passage 70 and ceramic filter 74 into nozzle 76 which impinges the gas stream upon buckets 83 of rotor 82 thus causing rotation of the rotor and modulation of the light rays along the optical path. When additional working fluid is needed for the turbine, then the heat absorbing material 55 may comprise a thermal decomposition material which decomposes endothermically into constituent gases. Alternately, this decomposition material may be embodied in the exothermic charge where it will be decomposed directly by the heat of the reaction. An example of such a material is poly-oxymethylene.

In the embodiments of the invention shown in the various figures, the graphite cone 17 or .46 serves both as a collector and emitter of infra-red rays; it is heated from both of its surfaces. The inner surface thereof is heated by direct contact with the reactant matter, while its outer surface receives heat radiation from the opposing surface of the graphite cavity. This construction has the further advantage of producing a black-body source of radiation close to unity.

Having thus described my invention, it is understood by those skilled in the art that various modifications may be made therein within the spirit and scope of the following claims.

What is claimed is:

1. A source of radiant energy, comprising a metal casing, said casing surrounding a lining of refractory material of low thermal conductivity, an exothermic chemical charge surrounded by said refractory material, means for igniting said charge, a graphite refractory cone having a geometrical configuration such as to produce an emissivity approaching unity, the substance composing said cone being of high thermal conductivity to permit rapid flow of heat therethrough.

2. A source of radiant energy as claimed in claim 1 further characterized in that there is provided a chamber containing a heat absorbing material adapted to reduce the internal pressure of the air entrapped therein.

3. A device for the emission of radiant energy in the infra-red spectrum, said device comprising a metal casing surrounding a cylindrical refractory lining, an exothermic chemical charge surrounded by said cylindrical refractory lining and having the ends thereof closed by a graphite cone at one end and by a chamber containing a gas producing material at the other end, characterized in that the said device is hermetically sealed at the boundaries of its component parts, and that substantially all air has been evacuated from the interior thereof.

4. A device as claimed in claim 2 in which said exothermic charge comprises a gas-producing material.

5. A device as claimed in claim 3, in which the said chamber contains a gas-producing material such as granular poly-formaldehyde.

6. A device as claimed in claim 1, in which there is provided a turbine wheel operatively connected with the gas chamber, said wheel being adapted to be driven by the gases from the exothermic reaction.

7. A device for emitting modulated radiant energy in the infra-red spectrum, comprising a charge of exothermic material, a graphite cone in juxtaposition with said charge, means for igniting said material, means for conducting the gaseous products. of said reaction through a bed of endothermic decomposition material, a turbine wheel, conduit means for impinging said gases upon said wheel, and a ceramic filtering means in said conduit.

8. A device as claimed in claim 7 embodying an optical reticle in gas driven rotor and an identical reticle in the stator the relative rotation thereby causing modulation of the light rays.

9. A device as claimed in claim 8 in which the reticle pattern of obscure and clear surface is arranged as to number and shape, so as to produce a characteristic modulation pattern or signature with each rotation.

References Cited by the Examiner UNITED STATES PATENTS Banca et al. 250-84 X RALPH G. NILSON, Primary Examiner. 

3. A DEVICE FOR THE EMISSION OF RADIANT ENERGY IN THE INFRA-RED SPECTRUM, SAD DEVICE COMPRISNG AMETAL CASING SURROUNDING A CYLINDRICAL REFRACTORY LING, AN EXOTHERMIC CHEMICAL CHARGE SURROUNDED BY SAID CYLINDRICAL REFRACTORY LINING AND HAVING THE ENDS THEREOF CLOSED BY A GRAPHITE CONE AT ONE END AND BY A CHAMBER CONTAINING A GAS PRODUCING MATERIAL AT THE OTHER END, CHARCTERIZED IN THAT THE SAID DEVICE IS HERMETICALLY SEALED AT THE BOUNDARIES OF ITS COMPONENT PARTS, AND THAT SUBSTANTIALLY ALL AIR HAS BEEN EVACUATED FROM THE INTERIOR THEREOF. 